Intervertebral implant with compressible shaped hollow element

ABSTRACT

An intervertebral implant for fusion of vertebral bodies is disclosed. The implant includes a flattened shaped hollow element in the form of a hollow cylinder, hollow truncated cone, hollow truncated pyramid, or hollow truncated wedge, with an outer surface having a flattened upper bone-contact face, flattened lower bone contact face, and two lateral faces. The upper and lower bone-contact faces can be elastically compressed towards the interior space of the hollow element in such a way that the maxi mum distance between the upper and lower contact faces can be reduced by 0.5 to 5.0 mm. The compressibility of the implant allows the insertion of the implant without the need for distracting the vertebras. After the implant is implanted, the engagement of an engagement lip with an interlock means prevents the compression of the implant.

FIELD OF THE INVENTION

The invention refers to an intervertebral implant for fusion ofvertebral bodies, particularly in the region of the lumbar part of thespinal column.

BACKGROUND

From the prior art there are already different types of suchintervertebral implants known though which show the followingdisadvantages:

to insert the implant in the intervertebral space the respectivevertebras must be expanded by means of suitable instruments; and

the implant is endangered of sinking in the end plates of the respectivevertebras.

SUMMARY OF THE INVENTION

The present invention relates to an intervertebral implant which isinsertable into the cleaned out intervertebral space in a controllablemanner without an expanding instrument.

The implant according to the present invention comprises a flattenedshaped hollow element with an outer surface having a flattened upperbone-contact face, a flattened lower bone-contact face, and two lateralfaces. The upper and the lower bone-contact faces are elasticallycompressible towards the interior space of the hollow element such thatthe maximum distance between the upper and the lower bone-contact faceis reducible by 0.5-5.0 mm.

The flattened hollow element can have the shape of a hollow cylinder,hollow truncated cone, hollow truncated pyramid or hollow truncatedwedge.

Dimensions, geometry and material should be chosen such, that themaximum distance H between upper and lower bone-contact face isreducible by 0.5-5.0 mm preferably 1-3 mm.

In case of application of a force of pressure of 12 Newton on the upperand lower bone-contact faces the maximum distance H shall be reducibleby 15% to 30% preferably 20% to 25%. The compressibility of the implantallows its insertion without having to apply an expanding instrument.

Therewith the advantage is reachable that a minimum expenditure of forceis necessary for the implantation and a controllable insertion of thecompressed implant is possible. A minimum invasive and open surgerytechnique is therewith applicable.

The large bearing area of the implant prevents its sinking in into theend plates.

A preferred embodiment of the invention consists therein, that in theinterior space of the hollow element an engagement lip is provided whichis engageable into an interlock means. In case of an engaged engagementlip the compressibility of the hollow element is neutralized again sothat a usual rigid implant results.

Bone splinters or bone replacement material can easily be filled intothe interior space of the frontally and backwardly open hollow elementand the implant securely be mounted with little operating steps.

To advance a quick ingrowing of the bone the implant is suitablyprovided with perforations preferably in the form of longitudinalapertures. The longitudinal apertures allow a control of the ingrowingof the bone by means X-ray images in case of a material which is notpermeable for X-rays.

For the improvement of the stability of position of the implant theupper and /or lower bone-contact face is provided with a threedimensional texture preferably in the form of longitudinal grooves.

Compared to the prior art the following further advantages of theimplant according to the invention accrue:

security against slipping;

improved permeability for X-rays; and

enhanced elasticity of the implant.

The invention and further embodiments of the invention are discussed inmore detail in the following by means of the partially schematicrepresentations of an embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The figures show:

FIG. 1 a perspectival representation of the implant according to theinvention in the compressible state with a loose engagement lip; and

FIG. 2 a cross-section through the implant according to FIG. 1 in thenon-compressible state with engaged engagement lip.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The intervertebral implant shown in FIG. 1 and 2 consists essentially ofa hollow element 1 in the shape of a hollow cylinder whose outer surface2 consists of a flattened upper bone-contact face 3, a flattened lowerbone-contact face 4 and two lateral faces 5.

The implant may be fabricated in a suitable metal (i.e. titanium), butparticularly also in a synthetic material tolerated by the body likepolyethylene.

The upper and the lower bone-contact faces 3 and 4 are elasticallycompressible towards the interior space 6 of the hollow element 1, suchthat the maximum distance H between the upper and the lower bone-contactface 3 and 4 is reducable, typically by 2 mm. This renders possible aneasy insertion of the implant into the intervertebral space.

The lateral faces 5 are provided with recesses in the shape oflongitudinal holes 12, which may be omitted when using a syntheticmaterial. The upper bone-contact face 3 and/or the lower bonecontact-face 4 is provided with perforations 8 as well as with a centralgroove 9.

In the interior space 6 of the hollow element 1 an engagement lip 10 isprovided, which is engageable in an interlock means 11.

In the following the clinical application is described in detail. Thehollow element 1 shown in FIG. 1 is grasped at by means of a suitablecompression tool, such that a force of pressure, typically 12 Newton,may be applied on the upper and the lower bone-contact faces 3 and 4which compresses the hollow element 1. In this state the implant isinserted into the emptied intervertebral space as ever possible withoutdistraction tools whereby the three dimensional textures 7 in the shapeof longitudinal grooves facilitate the leading of the implant and offera protection against a possible slipping.

The compression tool is removed and the engagement lip 10 is set uprightand engaged into the interlock means 11 such that the hollow element 1is not compressible any longer. The implant may now be filled with bonesplinters or bone replacement material.

What is claimed is:
 1. An intervertebral implant comprising a flattenedshaped hollow element defining an interior space within an outer surfacethat includes a generally flattened upper bone-contact face, a generallyflattened lower bone-contact face spaced by a maximum distance H fromthe upper bone-contact face and two lateral faces, wherein the upper andlower bone-contact face are elastically compressible towards theinterior space of the hollow element such that the maximum distance Hbetween the upper and lower bone-contact face is reducible by 0.5 to 5.0mm and wherein the interior space is open at anterior and posteriorends.
 2. The implant according to claim 1, wherein the lateral faceshave an arcuate shape and the maximum distance H between the upper andlower bone-contact faces is reducible by 1-3 mm.
 3. The implantaccording to claim 1, wherein a force of pressure of 12 Newton on theupper and lower bone-contact faces reduces the maximum distance H by 15%to 30%.
 4. An intervertebral implant comprising a flattened shapedhollow element defining an interior space within an outer surface thatincludes a generally flattened upper bone-contact face, a generallyflattened lower bone-contact face spaced by a maximum distance H fromthe upper bone-contact face, two lateral faces, an engagement lipprovided within the interior space of the hollow element, and aninterlock means provided within the interior space of the hollowelement, wherein the upper and lower bone-contact face are elasticallycompressible towards the interior space of the hollow element such thatthe maximum distance H between the upper and lower bone-contact face isreducible by 0.5 to 5.0 mm, and wherein said interlock means andengagement lip are configured and dimensioned such that the engagementof the engagement lip with the interlock means prevents the compressionof the upper and lower bone-contact faces.
 5. The implant according toclaim 1, wherein the lateral faces are provided with elongated aperturesto promote the formation of new bone.
 6. The implant according to claim1, wherein at least one of the bone-contact faces is textured tostabilize the implant.
 7. The implant according to claim 1, wherein atleast one of the bone-contact faces is provided with perforations topromote bone ingrowth.
 8. The implant according to claim 1, wherein atleast one of the bone-contact faces is provided with at least onecentral groove to facilitate compression of the implant.
 9. The implantaccording to claim 1, wherein the implant is made of a biocompatibleplastic material.
 10. The implant according to claim 1, wherein theimplant is coated with an hydroxylapatite of tricalciumphosphate (TCP).11. The implant according to claim 1, wherein the hollow element has theshape of a hollow cylinder, hollow truncated cone, hollow truncatedpyramid, or hollow truncated wedge.
 12. The implant according to claim6, wherein both bone-contact faces are textured.
 13. The implantaccording to claim 7, wherein both bone-contact surfaces includeperforations.
 14. The implant according to claim 8, wherein bothbone-contact faces include a central groove to facilitate compression ofthe implant.
 15. The implant according to claim 9, wherein the implantis made of polyethylene.
 16. An intervertebral implant comprising ahollow support member that defines an interior space within an outersurface that includes a generally flattened first bone-contact face, agenerally flattened second bone-contact face, and a pair of lateralfaces having an arcuate shape and connecting the first and secondbone-contact faces at a maximum distance H therebetween, wherein thesupport member is made of a biocompatible material which is sufficientlyresilient to allow the first and second bone-contact faces to beelastically compressible towards each other in the interior space uponthe application of force thereto to reduce the maximum distance H, withthe bone-contact faces attempting to return to their originalconfiguration when the force is removed and wherein the interior spaceis open at anterior and posterior ends.
 17. An intervertebral implantcomprising a hollow support member that defines an interior space withinan outer surface that includes a generally flattened first bone-contactface, a generally flattened second bone-contact face, a pair of lateralfaces having an arcuate shape and connecting the first and secondbone-contact faces at a maximum distance H therebetween, an interiorwall extending from the first bone-contact face toward the secondbone-contact face through the interior space, and interlock meansassociated with the second bone-contact face for receiving the wall,wherein the support member is made of a biocompatible material which issufficiently resilient to allow the first and second bone-contact facesto be elastically compressible towards each other in the interior spaceupon the application of force thereto to reduce the maximum distance H,with the bone-contact faces attempting to return to their originalconfiguration when the force is removed and wherein engagement of thewall and the interlock means after the bone contact faces return totheir original configuration prevents further compression of the firstand second bone-contact faces.
 18. The implant according to claim 16,wherein at least one of the bone-contact or lateral faces includes anaperture to promote bone ingrowth, and at least one of the bone-contactfaces includes a texture to stabilize the implant and at least onecentral groove to facilitate compression of the implant.
 19. The implantaccording to claim 16, wherein the support member has the shape of ahollow cylinder, hollow truncated cone, hollow truncated pyramid, orhollow truncated wedge, and is made of a plastic material so that themaximum distance H is reduced by at least 15% when the bone-contactsurfaces are compressed.